THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.

ERIN BURNETT, CNN ANCHOR: OUTFRONT, next, breaking news, the very latest on the investigation. What did Dzhokhar Tsarnaev tell investigators today about the roots of the Boston marathon bombings plan?

Plus, who is the man that may have been responsible for the brothers' alleged radicalization?

And blown away, if you can imagine shrapnel hitting your body before hearing the blast. Dr. Sanjay Gupta on why some near the bomb survived and others did not. Let's go OUTFRONT.

Good evening, everyone. I'm Erin Burnett. Tonight, we begin with breaking news. The Boston bombing suspect tells investigators that the wars in Iraq and Afghanistan were motivating factors behind the attacks.

In addition to those late breaking details, we are covering the terror attack on Boston from every angle tonight. In Boston, Jake Tapper with the very latest on what Dzhokhar Tsarnaev told investigators today.

Brian Todd with new details on where the bombers may have purchased their explosives and David Mattingly with new clues on what prompted Tamerlan Tsarnaev's radicalization right here in the United States.

And then, Nic Robertson is going to follow that trail overseas to Dagestan, a region known for radical Islamic insurgency and the place where Tamerlan spent six months last year doing what?

And Chris Lawrence tonight is in Rhode Island with new details about Tamerlan's wife, Katherine Russell. Finally, here in New York, Deb Feyerick with new information on Tamerlan's connection to a bizarre, unsolved triple murder case.

I want to begin though with Jake Tapper in Boston. Jake, what more have you learned about what Dzhokhar has been telling investigators? I know there have been several preliminary interviews and you've been getting sort of the nuts and bolts and details of exactly how they have been communicating and what he said.

JAKE TAPPER, HOST, CNN'S "THE LEAD": That's right, Erin. U.S. government official has relayed to me some of the news from Dzhokhar Tsarnaev in his discussions with investigators. We learned last night that he was talking about how there were no foreign terrorist organizations involved.

His brother was the driving force and that their general motivation was Jihadist in nature considering themselves to be under attack as Muslims and trying to fight back. That is what Dzhokhar has been telling investigators.

So I don't want to -- I want to make sure everyone understands, this is what he is saying. We are not saying anyone believes him, but this is what he is telling investigators.

In addition, we found out some more details. One of them that is the wars in Iraq and Afghanistan are part of the motivating factors, part of this Jihadist mind set, believing themselves to be under attack.

In addition, Erin, we also found out that, according to Dzhokhar, again, take it with a grain of salt, he and his brother were self- radicalized. They were radicalized by watching videos on the internet.

Now, among those videos it is told likely, likely from this government official that the preaching of cleric Anwar Al-Awlaki who was killed in a drone attack a few years ago that it is likely that those videos were part of the self radicalization.

Now there is also a report about this magazine called "Inspire," which is put out by an al Qaeda affiliate, which has had instructions in the past on how to make a bomb. Investigators are looking into whether or not that played a role in that. But they have not had any sort of conclusion as of right now -- Erin.

BURNETT: All right, well, Jake Tapper, thank you very much. As Jake said, the latest is that Dzhokhar is telling the investigators that the wars in Iraq and Afghanistan were motivating factors.

Yet another new detail as we try to piece together how this could have happened. I want to go to Brian Todd also in Boston for more on how this could have happened. Because Brian, we're also learning about a trip that Tamerlan Tsarnaev made to a fireworks store in New Hampshire in February.

Because a lot of people are saying, well, where did they get both the financial means, but also just the physical means to pull off this alleged attack? What did he buy on that trip?

BRIAN TODD, CNN CORRESPONDENT: Erin, we're told by William Wymer, who is the vice president of a company called "Phantom Fireworks" that Tamerlan Tsarnaev bought two reloadable mortar kits with 48 shells from their store in Seabrook, New Hampshire, on February 6th.

Seabrook, New Hampshire is about an hour north west of Boston. He bought, again, two reloadable mortar kits with 48 shells from that store on February 6th. He asked the clerk what's the loudest and biggest thing you have. He paid about $200 for all of that.

But what's key here is that a law enforcement official tells CNN that this is not enough, not enough to construct or set off the kind of explosion that occurred during the Boston marathon. So what did he use these for? That's not clear.

Some kind of -- we're told the kind of powder used in those explosives, in those types of fireworks may in fact not be the kind of gunpowder or explosive powder used in the explosion.

So some answers and maybe a connection between those fireworks that he bought and the explosion, not quite clear yet. But we do know he bought two reloadable mortar kits on February 6th, 48 shells, but not enough according to a law enforcement official to construct the kind of explosion that occurred in the Boston marathon.

BURNETT: All right, Brian Todd, thank you. But obviously a crucial development because we'll find out more about where they could have bought other explosives. And also, of course, where they bought the explosive they used to test and try out these pressure cooker bombs.

I want to go to Nic Robertson now. He's in Dagestan. Nic, you know, the other part of this -- you know, Jake has been reporting on how the suspect number two, the younger brother is saying that they were radicalized in the United States.

But we know the parents of the Tsarnaev brothers live where you are tonight. We know that the older brother visited for six months last year. There are allegations he met with extremists.

We know that when he returned home here to the United States, he posted a video featuring an Islamic militant named Abu Dijana. So what can you tell us about that video and that man so we can understand how important he might be?

NIC ROBERTSON, CNN SENIOR INTERNATIONAL CORRESPONDENT: Sure. Abu Dijana has now been killed by Russian security forces here in a major shootout, but Abu Dijana is a guy about the same age as Tamerlan, quite charismatic and quite sort of a young following, if you will, in this area.

Perhaps what is significant about him, he's not a major name on the world stage, if you will, in terms of Jihadist. So when Tamerlan goes back home to the United States, posts this video online, and he doesn't choose some major sort of Jihadist from this area, a well- known figure.

He uses somebody who is lesser known. So has he made contact with him? Has he made contact with some of his foot soldiers here? Why has he become influenced by him? This is an area where there are daily attacks by rebels against security forces here just in the past couple of days a police chief attack, survives the attack last week, one policeman killed, three injured in another major attack the week before a policeman and family attacked in a car bombing. There's this constant military threat going on while Tamerlan is here himself. There's a huge double suicide bombing, 12 people killed, in this area with these Jihadist attacks that are taking place and relatively small populations. So could he have met with him? Was there some kind of direct influence here? Those are the questions that people are asking right now. No hard answers as yet -- Erin.

BURNETT: All right, Nic, thank you very much, reporting live from Dagestan tonight.

And still OUTFRONT, a hearing on whether clues were missed by the FBI years and I'm not exaggerating here, years before the bombings took place.

Plus, investigators are talking to the attorneys of Tamerlan's American-born wife, but why are they not talking to her?

And what did the bombings have to do with the cold murder case involving the death of one of Tamerlan's friends? No one was charged in this triple murder. We have the story.

(COMMERCIAL BREAK)

BURNETT: Investigators in the Boston bombing case are tonight revisiting an unsolved crime from September of 2011. Let me explain it to you because this is truly bizarre. One of Tamerlan Tsarnaev's closest friends, Brandon Mass and two other people were brutally killed. Three murders and they were killed by having their throats slit.

So what does this case have to do with the Boston attacks? Deb Feyerick is with me now and has been investigating that. I mean, Deb, when I saw this, it seemed almost too bizarre that he could have actually known someone who was involved in this triple murder and I know they are trying to find out the case was never closed. What have you learned?

DEBORAH FEYERICK, CNN NATIONAL CORRESPONDENT: Yes, Erin. You know, what's fascinating about this entire thing is that a number of agents that are investigating the marathon bombing have now turned their attention over to this grisly triple homicide.

One of the reasons is because Tamerlan and one of the victims, they were best friends. They were sparring partners and by all accounts they were very, very close to one another. Well, that friend was killed back in September of 2011 and what's so interesting about it is that the way in which the individual was killed.

He actually had his throat slit and the district attorney saying that it really -- his head was -- the victim's head was pulled back and then the throat slit from ear to ear. Two other men also were there at the time and they, too, were killed in a similar way.

Now, why is this interesting? According to a source that we're speaking to, apparently Tamerlan Tsarnaev was one of the last people to see his friend alive. After that, about three months later, he decides to go to Russia.

So that's one of the reasons they are going back and they are looking at this because they do believe that the victims knew who the killers were and they are very clear to say killers, plural, that it wasn't just one individual that did this.

Because, you have to remember, this man, Brendan Mess, actually he was a mixed martial arts expert. So he would have been able to fight back had the situation presented itself. But instead, he was brutally killed along with two other people.

And one other thing, Erin, at the crime scene, investigators found the bodies of the victims strewn with marijuana and cash that you would have expected to have been taken during a robbery. That was left behind, several thousand dollars worth -- Erin.

BURNETT: I guess, that might imply some sort of an inside job or dispute among people working together. Do they have any idea what the motivation was? Was it some sort of a drug deal or not? Did investigators ever talk to Tamerlan when the crime actually first happened?

FEYERICK: You know, all good points. First of all, there's no indication that investigators ever spoke to Tamerlan. Now, it may have been that they were investigating this just as sort of a horrible, but just sort of a drug case.

There were no links at the time, but now investigators are going back and they are looking at every single thing that just seems out of the ordinary and clearly the fact that his best friend was killed in such a brutal way.

Just months before Tamerlan goes to Russia, that's one of the -- that's one thing that they want to re-examine. So investigators are now pouring over the files of that case -- Erin.

BURNETT: Wow, all right, truly a strange thing. Obviously, they are going to try to get to the bottom of that, too. Deb Feyerick, thank you very much.

And we have breaking news on this angle. Ashleigh Banfield is in Boston and spoke to the sister of one of victims of the 2011 murder that Deb's just been reporting on. Ashleigh, what have you just found out?

ASHLEIGH BANFIELD, CNN CORRESPONDENT: Erin, I'm just off the telephone with the sister of one of the murder victims in that 2011 murder, in the triple homicide that Deb Feyerick was just telling you about. I just got off the phone with her. There are couple things that she can confirm to me, and that is this. That the district attorney in Middlesex County has been in touch with her. She's meeting with them next week. (INAUDIBLE) investigators on that case are meeting with her and have been speaking with her since Saturday.

Not only that, she confirms to me that the same detectives are still on that case and that they are detectives that she has spoken with. Specifically they asked her this: what can you tell us about your brother's relationship with Tamerlan, the now-dead suspect in the Boston bombings? So, there is an (INAUDIBLE) connection that they're trying to figure out if there is any.

But these are the questions they asked of her. She felt like she couldn't really enlighten these detectives at all because she felt her brother wasn't a good friend or even a friend at all or even an acquaintance at all of Tamerlan Tsarnaev. However, she does think this is a good development at least in the 18-month-old case of her brother's murder and those of his two friends, murdered alongside him. She feels like perhaps this will bring national attention and eyes all over this jurisdiction and neighboring county. (INAUDIBLE) they will be able to get some kind of resolution. (INAUDIBLE)

BURNETT: All right. Thanks very much to Ashleigh Banfield. Hopefully you could hear all of that. Obviously, we're having a little bit of audio difficulty. But it was important. I wanted to make sure you could hear it as best as we could.

Still OUTFRONT, investigators believe Tamerlan had a very strong influence over his younger brother. And tonight, a psychologist joins us if one person can really convince another to do terrible things. Is that a legitimate explanation or not?

And up next, did the FBI drop the ball when Tamerlan Tsarnaev could have been stopped? There was a point he could have been stopped, but could the FBI have been the ones to do it? Rep. Mike McCaul, chairman of the Homeland Security committee is next.

(COMMERCIAL BREAK)

BURNETT: The FBI is facing tough questions tonight about whether federal agents missed critical clues during their investigation of Tamerlan Tsarnaev, even after Russia raised a red flag about his radical Islamic views two years ago. Speaking before the Senate Judiciary Committee, Homeland Security Secretary Janet Napolitano acknowledged today that the government was aware of Tamerlan's trip to Dagastan last year, a volatile region in Russia has been plagued with radical violence.

(BEGIN VIDEO CLIP)

SEN. CHUCK GRASSLEY (R), IOWA: Was your department aware of his travels to Russia and if you weren't, the reason?

NAPOLITANO: Yes, the system pinged when he was leaving the United States. By the time he returned, all investigations had been -- the matter had been closed.

(END VIDEO CLIP) BURNETT: Did the agency drop the ball? The question keeps building. Congressman Michael McCaul, chairman of the House Homeland Security Committee, is OUTFRONT tonight. Good to see you, sir. Now as you know, the FBI says it looked into Tamerlan before that recent trip to Russia at the behest of the Russians and found nothing derogatory.

But according to some reports, Russia didn't stop there and as recently as November of last year, Russia's secret service alerted the FBI about Tamerlan's having alleged contact with a suspected militant. Now, the "Wall Street Journal" says the FBI disputes this. They said, look, we didn't get an alert. But I ask you, what did you know about whether Russia warned the United States again about Tsarnaev's extremist ties?

REP. MICHAEL MCCAUL, CHAIRMAN OF HOMELAND SECURITY COMMITTEE: The FBI told me that they were not warned again. But let's look at the facts here. The FBI has denied they had any knowledge of his trip to Russia. They had a lead opened on this individual that they closed, and now we have the secretary of Homeland Security testifying that they knew he left and traveled to Russia.

When you look at the original Russian intelligence wire, it basically indicates that this is a more dangerous person that may leave the United States and join underground extremist groups. So the idea when that flag went up, what was done with that information? The Department of Homeland Security was created after 9/11 to make sure we didn't have this happen again, that the dots would be connected, that people would communicate. And the problem is, DHS had this information, and presumably the man on the JTTF CVP knows about this. And the question that can't be answered right now when asked the director, is did the FBI know about this? And if he didn't know, why didn't he?

BURNETT: Right. And after the visit to Russia, Tsarnaev then, as we understand at that point, came home and posted a lot of videos, including one from a radical Muslim cleric called Fayez Muhammed. Did the FBI miss something or not by following up on that? I mean, this is somebody that they do admit at this point had been He was on their radar and they dismissed him. But then he's posting radical videos.

MCCAUL: When you mention was a ball dropped, I think the idea that they did know about his Russian travel, the idea that maybe DHS did not share that information with the FBI. After all we've been through after 9/11 and talking about connecting the dots -- and just maybe, if they did know that, wouldn't they have reopened that lead that they closed?

Now, I was told that the case was closed, there's nothing derogatory. But it seems to me if you know he's traveling back to Russia after Russia has warned the FBI of his behavior, it seems to me you could have reopened that lead and just maybe this could have been prevented.

BURNETT: And there's a lot of people asking that question tonight, Chairman. You know, but in the past, the FBI has interviewed, investigated other people who have gone on to successfully commit attacks on U.S. soil. You know, an agent interviewed Abdulhakim Muhammad. He's serving a life sentence for killing an Army private at a recruiting station, of course. And it also investigated Army Major Nidal Hasan, charged with killing 13 people at the horrible Fort Hood, Texas, shooting.

This is a difficult question to ask, but they are investigating thousands of people. Is it acceptable or basically inevitable that someone is going to fall through the cracks?

MCCAUL: Well, in fairness to them, and I know working with the JTTFs in the past, they have thousands of leads coming in all the time.

BURNETT: Yes.

MCCAUL: But as you mentioned in our letter to the secretary, to the director of the FBI and to DNI director Clapper, we raised the issue that you raised. Five individuals -- key individuals that were able to, in most of the cases successfully pull off a terrorist attack that really slipped through the cracks and off their radar.

And my job as the chairman of Homeland Security is to examine what happened, what possibly what went wrong and how can I correct that in the future, which is why we intend to hold hearings on this issue.

BURNETT: And a final question, sir. The younger brother, Dzhokhar, is saying they acted alone. It's unclear whether that's just what he's saying or whether that's actually true. There are reports that the older brother met with extremists during that trip to Dagestan and there are a lot of other questions right now about how he became a radical. Do you think they truly acted alone at this point?

MCCAUL: I find that difficult to believe. I also find the idea that there wasn't any foreign connection difficult to believe. When you look how sophisticated these bombs were that they made, most of the experts I've talked to indicate that there had to be some sort of trainer who trained them in this. And some training ground that they went to to test these explosives.

And whether that happened over in Chechen region or whether that happened in the Boston area, we don't know the answer to that. But it is the job of the FBI and Homeland Security to cast a wide net to make sure if there's anybody else involved with this horrible bombing, that we catch them.

BURNETT: Chairman, good to talk to you again. We appreciate it. You heard the chairman say, he finds it difficult to believe they acted alone or without foreign influence.

Still to come OUTFRONT, how did they the brothers become radicalized? We have a special OUTFRONT investigation tonight.

Plus, the wife of Tamerlan Tsarnaev and why she is not talking to investigators. And just in, the man who went out to look at his boat and found the man at the center of the citywide manhunt. The moment of discovery in his own words.

(COMMERCIAL BREAK)

BURNETT: We have new details tonight about what motivated Dzhokhar Tsarnaev and his brother Tamerlan to allegedly carry out the Boston marathon terror attack in which three were killed, more than 260 were injured.

Now, according to a government official, Dzhokhar Tsarnaev has told investigators the wars in Afghanistan and Iraq were the reason he and his brother Tamerlan decided to set off the deadly bombs. Dzhokhar in a report has also told investigators that the brothers were self-radicalized. Again, this is what he's saying.

But how could these two Chechen immigrants have become jihadists?

Our David Mattingly is OUTFRONT with the story.

(BEGIN VIDEOTAPE)

DAVID MATTINGLY, CNN CORRESPONDENT (voice-over): Eyewitness photographs captured the violent street shootout and the last moments of a desperate and dangerous Tamerlan Tsarnaev.

A federal law enforcement source tells CNN Tsarnaev's own brother conveyed to investigators he was not only the mastermind behind the Boston bombing but he was motivated behind a jihadist call for retaliation for so-called attacks on Islam, a self-made radical with a wealth of information at his fingertips.

DANA JANBEK, LASELL COLLEGE: There are over 8,000 websites that are -- that have very extremist radical ideology.

(on camera): How many of these offer explanations or instructions on how to build weapons?

JANBEK: Some of them do.

MATTINGLY (voice-over): A senior administration official says investigators are trying to determine if the online "Inspire" magazine published by al Qaeda in Yemen could be one of the site's possibly providing the blueprints for the bombs Tsarnaev used. But there are doubts that Tsarnaev could have built the devices successfully without some kind of training.

BOB BAER, FORMER CIA OPERATIVE: The fact that five of his bombs went off is as extraordinary piece of luck or he knew what he was doing. I don't see any middle way.

MATTINGLY: CNN analyst Bob Baer believes Tsarnaev could have had personal contact and training with jihadists when he visited his parents in Russia early last year. Social media may provide a clue.

After returning to the U.S., a video of an Islamic militant known as Abu Dudzhan was posted and then removed from Tsarnaev's YouTube channel.

BAER: He listened to somebody there. He maybe got some sort of training, or at least people build this stuff, something -- there's something we're missing. I just have an uneasy feeling about it. But not having the facts, I can't, you know, assure you 100 percent.

MATTINGLY: A U.S. government official tells CNN Tsarnaev's brother claims they had no contact with any foreign terrorist organization. And online preachings of Anwar al-Awlaki are likely influence. But as hard answers behind his radicalization prove elusive, there is no doubt in Tsarnaev's ability to conceal the sinister plans from those closest to him, his parents and even his wife.

MIRIAM WEIZENBAUM, ATTORNEY FOR BOMBING SUSPECT'S WIFE: A report of involvement by her husband and brother in law came as an absolute shock to them all.

(END VIDEOTAPE)

BURNETT: All right. Obviously, the statement from the attorney of the wife, his wife, though, wasn't the only one expressing dismay over his actions. You also heard from his sisters, right?

MATTINGLY: That's right. Hearing from the sisters today as well, they speaking through their attorney releasing a statement saying that they were dismayed as well, expressing sorrow over what they saw, calling it a callous act and said, we don't have any answers but we look forward to a thorough investigation and hope to learn more -- the same position just about everyone close to these two men are taking today.

BURNETT: And, David, does the family have any -- I mean, we're all just trying to find out when they were radicalized. I know the younger brother is saying, well, it happened here in the U.S. but there are certain pieces of data that indicate that may not be totally the truth. Does the family have theories about what happened to Tamerlan Tsarnaev, when he became a, quote-unquote, "jihadist"?

MATTINGLY: Well, CNN has heard from their uncle here in the U.S. He spoke extensively about his thoughts on this. He said there was one man in particular, someone who converted to Islam, an Armenian who live here, immigrated to the U.S. and that he had a lot of influence over the older brother a couple of years ago, but no evidence actually of any radicalization from that individual, just someone who got him to go back to start worshipping again and become more devout.

The actually radicalization, and everything we're hearing right now coming from the investigation and coming from his younger brother, is that the older brother here became radicalized simply by what he was seeing on the Internet.

BURNETT: David Mattingly, thank you.

Well, federal investigators are trying to piece this together, trying to get answers. And they are talking to lawyers for Tamerlan Tsarnaev's widow. But why are they not talking to her directly? After all, they talked to his sisters, a lot of other people?

According to her attorneys, the 24-year-old Rhode Island native is cooperating with the investigation and knew nothing about the bombings. It's still unclear exactly what she did know. Our understanding, of course, as our Chris Lawrence has reported, is that she seemed to have been living with him in Boston with their young daughter in the time leading up to and when this happened.

Chris Lawrence is in Rhode Island tonight with the latest.

And, Chris, I know her attorneys are talking to the FBI. But why isn't she?

CHRIS LAWRENCE, CNN PENTAGON CORRESPONDENT: Well, if she is, Erin, her lawyers certainly are not admitting that publicly. Basically, the lawyers are telling us that they are talking to the investigators on her behalf but they won't confirm whether Katy Russell herself has spoken with those authorities directly, one on one.

Now, that said, she wants to get to the bottom of this and has nothing to hide.

(BEGIN VIDEO CLIP)

AMATO DELUCA, ATTORNEY FOR BOMBING SUSPECT'S WIFE: She is doing everything she can to assist in the ongoing investigation.

WEIZENBAUM: The injuries and loss of life to people who came to celebrate a race and a holiday has caused pr profound distress and sorrow to Katy and her family. The reports of involvement by her husband and brother-in-law came as an absolute shock to them all.

(END VIDEO CLIP)

LAWRENCE: So much of a shock that the attorneys say Katy last saw her husband on Thursday when she left for work and that the husband was home with their young daughter. That was, of course, before the FBI released those videos and pictures that set off this manhunt, Erin.

BURNETT: And, Chris, before the video came out but after the act happened. And on that, I want to ask you something. I mean, you know, she was living in a very cramped apartment in Cambridge. The pictures we've been shown appear to be cluttered. That they had explosives, they had pipe bomb materials. They had all this stuff going on. How is it possible she lived there and did not know that something was amiss?

LAWRENCE: I think you've hit on the big reason why investigators really want to talk to her as they try to piece together exactly when and where Tamerlan may have tried to assemble some of those bombs.

The lawyers will say that, (a), she didn't speak Russian so she didn't always understand everything that was being said. They also say that she spent a lot of time out of the house. Sometimes up to six, seven days a week, 70 hours working as a home health care aide, so she wasn't there very much and really didn't spend a whole lot of time around the younger brother who was back and forth to UMass.

BURNETT: She was working incredibly hard, as we've reported.

Thanks very much to Chris Lawrence who's been doing the legwork on reporting on Tamerlan Tsarnaev's wife.

Well, according to government officials, the Tsarnaev brothers became self-radicalized by their own accord, at least that's what the younger brother has said so far in interviews from his hospital room. But how did men end up taking the path and did they record others?

OUTFRONT tonight, Steve Hassan. He's been counseling people with radical personal changes and extreme behavior for more than three decades, as a director of Freedom of Mind Research Center.

Thank you so much.

I'm really glad to talk to you because everything we have heard seems to indicate -- and I want to emphasize -- seems to indicate that this happened over a relatively short period of time, whether it was a few years or a year, it happened very quickly, that they went from being normal, all-American kids, even more recently, the younger brother out partying, having fun with his friends and then, all of a sudden, becomes a jihadist.

Does this happen just from the internet?

STEVE HASSAN, MIND CONTROL EXPERT: It doesn't -- I don't think that the older brother was recruited just from the Internet. The latest information confirms my suspicion that in fact there was a person who began indoctrinating the older brother.

But I just want to say when I was recruited into a cult in 1974, it took two weeks for me to drop out of college, quit my job, donate my bank account and believe that the messiah was on Earth.

So, yes, it can happen very fast.

BURNETT: I mean, that's incredible. You say that and it brings to mind Katherine Russell. We've shown pictures of her in high school, A-student, graduating college, she wanted to join the Peace Corps. Those are her goals. That's her then. She changed dramatically to marry Tamerlan Tsarnaev. She dropped out of school. She started wearing the head scarf, the hijab, converted to Islam. She changed her life, had a baby instead of finishing college.

Is that -- some people might say, you know what? That's the choice some people make.

HASSAN: Stereotypical, Erin.

BURNETT: Is it healthy or not?

HASSAN: It's a stereotypical scenario of an undue influence situation, in my opinion. And what people don't understand is that intelligent, educated people can be deceptively recruited, incrementally often, with hypnosis, with different type of mind control techniques, behavior control, information control, phobias can be installed in people's minds very fast. And systematically, step by step.

No one in my 36 years of experience says I want to join a destructive cult and blow up people. But people do fall in love with people, and then they recruit them and indoctrinate them or they meet a comrade and step by step they get indoctrinated. And then family members and friends witness this personality change, but then are frozen because they don't know what to do to help their loved one.

BURNETT: So, the thing that I just haven't been able to get my mind around at all, among many things, but one of them is how the younger brother, Dzhokhar, 19 years old, goes back to school, goes to the gym, goes to parties and in his dorm for three days as if nothing happened. In fact, he's even there Thursday when the video comes out. As if nothing had happened. That's what everyone says, as if nothing had happened.

How is that possible? He had just killed people.

HASSAN: It's very, very understandable if you understand the paradigm of dissociative disorder and the cult depresses a person's real identity. And if he was instructed by his brother, the indoctrinator, to go back to school and pretend like nothing has happened, and act normally, then he's going to go back to school and act normally. Completely stereotypical behavior, in my opinion.

BURNETT: Wow, just incredible to me to try to comprehend that.

Thank you so much, Steven. We appreciate your time tonight.

And still, OUTFRONT, the destructive force of a pressure cooker bomb. Exactly how it explodes and what it means for the people who are closest to it.

Plus, the man who owns the boat where Dzhokhar Tsarnaev was hiding speaks out for the first time. What he saw and what it did to him, in his own words.

(BEGIN VIDEO CLIP)

DAVID HENNEBERRY, BOAT OWNER WHO DISCOVERED DZHOKHAR: If the people that were killed can get some --

(END VIDEO CLIP)

(COMMERCIAL BREAK)

BURNETT: And we have breaking news. The Justice Department has formally tonight filed its case against Lance Armstrong for millions of dollars, which the U.S. Postal Service had spent to sponsor the cycling team. The USPS paid approximately $40 million to sponsor the team, according to the court document.

There had been a lot of questions whether the government would go ahead with this and we can confirm that they have.

Well, David Henneberry was the man who tipped the officials to the whereabouts to Dzhokhar Tsarnaev. And he's speaking out for the first time. Some time on Thursday night, Dzhokhar, injured with gun shot wounds, found refuge in a boat that was parked in the backyard. That boat belonged to Henneberry whose home remains a crime scene. He isn't been allowed back in since then.

In an exclusive interview with our affiliate, WCVB, Henneberry clears up how he stumbled on Dzhokhar that night.

(BEGIN VIDEOTAPE)

HENNEBERRY: I know people say there's blood in the boat, he saw blood and went in. Not --

REPORTER: Not true?

HENNEBERRY: Not true. No.

REPORTER: The word is, you saw the boat, you pulled back the wrapping, you saw a body, it moved and you called 911?

HENNEBERRY: Oh, no, no, no.

REPORTER: No?

HENNEBERRY: No, no, no.

REPORTER (voice-over): So he went to the garage and got a step ladder.

HENNEBERRY: I got I think three steps up the ladder and I was -- I rolled it and I can see through the shrink wrap. I didn't expect to see anything and I look in the boat over here on the floor and I see blood and --

REPORTER (on camera): A lot of blood?

HENNEBERRY: Good amount of blood. REPORTER: Yes.

HENNEBERRY: And my eyes went to the other side of the engine box. The engine box is in the middle -- there was a body.

REPORTER: And at that moment, what did you do? What were you thinking at that moment?

HENNEBERRY: Oh, my God.

REPORTER (voice-over): He couldn't see suspect number two's face. He was glad he couldn't see his face.

HENNEBERRY: Well, I know I took three steps up the ladder. I don't remember stepping down off the ladder. This hits you more afterwards when you think, my God, we probably slept last night. This guy could be -- that -- you know, I don't know. It's just -- it's surreal.

REPORTER: In that instant, police responded and he and his wife were taken away.

(on camera): People are calling you national heroes.

HENNEBERRY: If the people that were killed can get some --

REPORTER: You know, in many ways, they do.

HENNEBERRY: Then I'm at peace with it, you know.

(END VIDEOTAPE)

BURNETT: The man who made the call that night. And without him, law enforcement officials have said they wouldn't have found Dzhokhar that night.

Let's check in with Anderson Cooper with a look at "A.C. 360".

Hey, Anderson.

ANDERSON COOPER, CNN ANCHOR: Hey, Erin. Yes, we're going to play more of that remarkable interview of the boat owner.

We're going to be covering the breaking news, there's a span of days a man who in the span of days witnessed and survived both the horrors of the Boston marathon and the fertilizer plant explosion in West, Texas. We're going to hear his incredible story. Joe is his name, this incredible story ahead.

Plus, details of the breathtaking images of the police shootout with the two bombing suspects. It's all ahead at the top of the hour, Erin.

BURNETT: All right, Anderson, we look forward to seeing you in a few moments from Boston. More than a week from the bombings, 50 victims are hospitalized tonight. 13 have had amputations and three lost their lives. The destruction of two crude homemade devices. The pressure cooker detonator explodes with force, propelling thousands of sharp, searing objects through the air. Explosive experts in a New Mexico test range detonated a similar device for our David Mattingly to show us the deadly force.

Here it is.

(BEGIN VIDEO CLIP)

UNIDENTIFIED MALE: Four, three, two, one.

(EXPLOSION)

DAVID MATTINGLY, CNN CORRESPONDENT: How fast were these things moving when they out of there?

VAN ROMERO: They can travel 1,000, 2,000 feet a second.

MATTINGLY: A second? That's faster than sound.

ROMERO: Right. They'll move faster than the speed sound. These things will actually get in front of the shock wave and hit you before the pressure wave does.

MATTINGLY: You're hit before you could hear it.

ROMERO: That's right.

(END VIDEO CLIP)

BURNETT: Hit before you even hear it. Faster than the speed of sound.

Look again, this time through the lens of a high speed camera at the ripples. See those ripples traveling across the sand? That shows the impact of the shock wave as it moves out. In Boston, the packed marathon spectator crowd was right for maximum carnage.

Dr. Sanjay Gupta joins me now to explain the injuries.

I mean, on some level when you think about how many people were around, so many people are seriously injured, whose lives have been devastated forever. Three people are dead.

When you look at that do you think this was the maximum damage it could have done or could this have been a lot worse?

DR. SANJAY GUPTA, CNN CHIEF MEDICAL CORRESPONDENT: Well, it's a good question. And when you think about these types of devices, David showed what was in that particular pressure cooker, we know from talking to doctors there were carpenter nails, there was this BB-like devices. They get a huge amount of force in the pressure cooker. And then it's indiscriminant, Erin. I think that's one of the things that doctors said as well. Just indiscriminant in the way that it travels obviously very fast, and they're behaving in some ways like bullets. It can cause all sorts of different injuries, and it's really hard to predict. Yes, it could have been a lot worse to answer your question.

One thing I will say -- when you fire a gun or a bullet, it's designed to travel at a certain speed, to go in a certain direction, maybe to tumble when it hits the body. This is like a scatter shock of things. You just don't know what you're going to see.

BURNETT: Right. David Mattingly also talked about you hear it after it hits you. It goes faster than the speed of sound, which is just -- you know, maybe something we wouldn't all necessarily realized it first glance. But are the injuries you get from these pieces of shrapnel, which are often distorted and twisted, I mean, unlike a bullet that has a firm shape to it, is this worse than you would get from a bullet?

GUPTA: It can be. But, you know, the thing about this -- just keep in mind with bullets, even the bullets sometimes are designed to do all sorts of things in the body, like tumbled, do all sorts of things. These bits can sort of do the same thing.

So you get the primary blast which David was talking about. That can cause injuries that you don't even see. It can do things to your intestine, to your eardrum. Then you get that secondary blast, sometimes right on top of each other because the shrapnel is moving so fast and they can penetrate all these areas of the body.

Now, the BBs or the ball bearings that David was describing and the doctors were describing in Boston are perhaps the most concerning. They can really penetrate, as one doctor said, they can penetrate through the chest and go through the heart, a very, very smart wound. You may not even see it because of a deadly injury somewhere within the chest cavity. So --

BURNETT: So, don't see all the injuries that you may necessarily get.

GUPTA: No. And that's what sometimes so difficult for doctors, I think either in an urban setting like this, or in war zones because what happens is someone comes in and they looks or war zones. People come in and they look like they may be relatively OK. But they may have a small piece of shrapnel that caused a tear in a blood vessel and they're starting to bleed.

BURNETT: Which could probably be impossible to remove.

GUPTA: You wouldn't know to where to look. There are people who are walking around who have over 100,000 pieces of shrapnel in their body.

BURNETT: Who don't know it?

GUPTA: They may not know it.

BURNETT: Wow.

GUPTA: There maybe no point in taking that out. A lot of those people coming back from warzones.

BURNETT: Sanjay, thank you very much.

GUPTA: Thank you.

BURNETT: Up next. He was accused of sending ricin to the president and a member of Congress. You know what? He was released, claims he was framed. The story in his words, next.

(COMMERCIAL BREAK)

BURNETT: A startling twist today in the ricin investigation, which you may have thought was over. No, not even beginning.

The man arrested for allegedly sending mail containing the deadly poison to the president and a U.S. senator last week was suddenly released with all the charges dropped.

Dan Lothian is OUTFRONT with the details.

And, Dan, what happened?

DAN LOTHIAN, CNN WHITE HOUSE CORRESPONDENT: You know, I think that's the question that everyone is asking tonight. We saw the government's case starting to unravel earlier today. They were in the third day of the preliminary hearings for 45-year-old Paul Curtis when suddenly the proceedings were halted. No reason given.

And then a short time later, Curtis was released on bond. Prosecutors were not saying what was behind all of this. It was clear though, at that time, that this case was unraveling.

You know, all along from the beginning, Curtis, his attorneys, his legal team had been saying that he was innocent. They felt that he was framed, that there's a lot of information out there in social media. Whether it's Facebook or other places where they could have gotten his writings and made it appear that he was behind the letters sent to the president and to the senator.

And today, shortly after the announcement was made that the charges would be dismissed, the case would be dropped, then Curtis came out and spoke to the media.

(BEGIN VIDEO CLIP)

PAUL KEVIN CURTIS, FORMER RICIN SUSPECT: I respect President Obama. I love my country and would never do anything to pose a threat to him or any other U.S. official. This past week has been a nightmare for myself and my family. My mother has suffered, as well as my children. I would like to get back to normal.

(END VIDEO CLIP)

LOTHIAN: And now we wait to find out what the government will do next. All indications are they're looking at another suspect -- Erin.

BURNETT: All right. We're obviously hoping that will get solved. And, of course, Mr. Curtis, there's a lot of frustration. He's an Elvis impersonator and worried he's not going to get hired due to all of this.

Our continuing coverage of the bombings continues right now in Boston.